Scientists from the National University of Singapore (NUS) have identified a crucial DNA “switch” that enables tropical butterflies to modify their wing eyespot sizes in relation to seasonal temperature variations. The research, published in the journal Nature Ecology & Evolution on October 24, 2025, reveals insights into the evolutionary mechanisms behind environmental adaptability in these insects.
The ability of butterflies to change their appearance with the seasons, known as plasticity, plays a significant role in their survival, yet its evolutionary basis has long puzzled scientists. A research team led by Professor Antónia Monteiro from the NUS Department of Biological Sciences, focused on the African butterfly species Bicyclus anynana, which exhibits notable differences in wing patterns between the wet and dry seasons.
During the wet season, these butterflies develop larger eyespots on their wings, whereas the dry season brings smaller eyespots. Such changes enhance their chances of survival in varying environmental conditions. Previous studies indicated that the temperature at which caterpillars are raised significantly influences these size alterations, a response particularly evident in the satyrid group of butterflies known for their brown wings adorned with distinct eyespots.
In this groundbreaking study, the researchers pinpointed a master gene called Antennapedia (Antp), which regulates the development of eyespots in satyrid butterflies. The expression of this gene varies depending on the temperature conditions during the butterflies” development. When the activity of this gene was disrupted in two different satyrid species, the size of the eyespots diminished, especially under warmer rearing temperatures, confirming Antp”s essential role in seasonal size adjustments.
Furthermore, the team discovered a novel DNA switch, referred to as a “promoter,” which is exclusive to satyrid butterflies. This switch activates the Antp gene in specific eyespot cells. When the switch was disabled, the butterflies” capability to modify their eyespot sizes in response to temperature was compromised, indicating its significance in the evolution of seasonal adaptability.
Dr Tian Shen, the lead author of the study, noted the remarkable nature of a simple genetic switch being responsible for complex environmental sensitivity across a wide array of insects. He emphasized that these findings pave the way for future research into the roles of such genetic switches in adaptation, with potential implications for conservation efforts in the face of climate change.
